Control valve for variable capacity compressors

ABSTRACT

There is provided a control valve for a variable capacity compressor, which is applicable to a compressor of large capacity. This control valve comprises a valve main body ( 20 ) equipped with a valve rod ( 15 ) having a valve body ( 15   a ), with a valve chamber ( 21 ) having a guide hole ( 19 ) in which the valve rod is enabled to slide and a valve aperture ( 22 ) for the valve body, with a cooling medium inlet port ( 25 ) disposed on an upstream side of the valve aperture for introducing a cooling medium from the compressor, and with a cooling medium outlet port ( 26 ) disposed on a downstream side of the valve aperture and communicated with a crank chamber; an electromagnetic actuator ( 30 ) for driving the valve rod to move in the direction of opening or closing the valve aperture; and a pressure sensitive moving member ( 40 ) for driving the valve rod to move in response to a sucking pressure of the compressor; which is characterized in that a contracted hole portion is formed at an upper portion of the guide hole, that a diametrally reduced rod portion ( 15   b ) to be inserted into the contracted hole portion ( 19   b ) is formed at an upper portion of the valve rod, and that the valve rod is provided with an equalizing hole ( 51 ) for introducing a cooling medium pressure of the cooling medium outlet port into an equalizing pressure introducing chamber ( 52 ).

FIELD OF THE INVENTION

The present invention relates to a control valve for a variable capacitycompressor to be employed in an air conditioner for vehicle. Inparticular, the present invention relates to a control valve for avariable capacity compressor, which is applicable to a compressor oflarge capacity while making it possible to share the components employedin the conventional control valves.

BACKGROUND INFORMATION

A control valve for a variable capacity compressor to be employed in anair conditioner for vehicle is generally constructed as follows. Namely,a cooling medium exhibiting a discharge pressure “Pd” is permitted toenter into the crank chamber of compressor from the discharge chamber ofcompressor so as to adjust the pressure “Pc” inside the crank chamber.In this case, the flow rate of cooling medium exhibiting a dischargepressure “Pd” to the crank chamber is restricted in such a manner thatthe quantity of supply (throttling volume) of cooling medium to thecrank chamber can be controlled depending on the sucking pressure “Ps”of compressor. For this purpose, various proposals where anelectromagnetic actuator (solenoid) is employed have been suggested orput into practice as seen from JP Patent Laid-open Publication (Kokai)No. 2002-303262 (2002).

FIG. 3 illustrates one example of such a conventional control valve fora variable capacity compressor. The control valve 5 shown hereincomprises a valve rod 15′ having a valve body 15 a; a valve main body20′ provided with a valve chamber 21 having a valve seat (valveaperture) 22 with which the valve body 15 a is enabled to retroactivelycontact, with a plurality of filter (25A)—attached cooling medium—inletports 25 for receiving a cooling medium of discharge pressure “Pd” fromthe compressor, these inlet ports 25 being disposed around the outercircumferential wall of the valve chamber 21 (i.e. an upstream side ofthe valve seat 22), and with a cooling medium outlet port 26 which isdisposed on a downstream side of the valve seat 22 and communicated witha crank chamber of the compressor; an electromagnetic actuator 30.

This electromagnetic actuator 30 is equipped with a coil 32 having aconnector 31 for electroexcitation, with a cylindrical stator 33disposed on the inner peripheral side of the coil 32, with a suckingmember 34 having U-shaped cross-section and press-inserted into a lowerinner peripheral end portion of the stator 33, with a flange (35a)—attached pipe 35 which is coupled, through an upper edge portionthereof and by means of TIG welding, to a lower outer circumferentialend portion (step portion) of the stator 33, with a plunger 37 slidinglydisposed so as to enable it to move up and down inside the guide pipe 35and placed below the sucking member 34, and with a cylindrical housing60 with an opening in its bottom and disposed to cover the outerperiphery of the coil 32.

Additionally, a hexagon socket head adjusting screw 65 is screwed on anupper portion of the stator 33. A pressure sensitive chamber 45 intowhich the sucking pressure “Ps” of compressor is to be introduced isformed between the adjusting screw 65 attached to the inner peripheralwall of stator 33 and the sucking member 34. In this pressure sensitivechamber 45, there is disposed, as a pressure sensitive driving member, abellows main body 40 consisting of a bellows 41, a downwardly projectedupper stopper 42, a reverse U-shaped lower stopper 43 and a compressioncoil spring 44. Further, a compression coil spring 46 for urging thebellows main body 40 to contract (in the direction to contract it towardthe adjusting screw 65) is interposed between the bellows main body 40and the sucking member 34. Further, a step-attached operating rod 14piercing through the sucking member 34 is interposed between the reverseU-shaped lower stopper 43 of bellows main body 40 and a U-shaped portion37 c of plunger 37. Additionally, a valve-opening spring 47 made of acompression coil spring for urging the valve rod 15′ downward (in thedirection to open the valve) by way of the plunger 37 is interposedbetween the sucking member 34 and the U-shaped portion 37 b of plunger37.

On the other hand, a convex stopper 28 for regulating the lowermostdescending position of the plunger 37 is projected upward from an uppercentral portion of the valve main body 20′. A guide hole 19 in which thevalve rod 15 is slidingly inserted is formed at a central portion ofvalve main body 20′ over the valve chamber, this guide hole 19 beingformed so as to pierce also through the convex stopper 28. A suctionpressure cooling medium-introducing chamber 23 for enabling a coolingmedium of suction pressure of the compressor to be introduced therein isformed between the plunger 37 and an upper outer periphery of the valvemain body 20′ (an outer peripheral wall of the convex stopper 28). Aplurality of suction pressure cooling medium-introducing ports 27 areformed in the outer wall of the suction pressure-introducing chamber 23.A cooling medium of sucking pressure “Ps” that has been introduced intothe suction pressure cooling medium-introducing chamber 23 from thecooling medium-introducing ports 27 is designed to be introduced intothe pressure sensitive chamber 45 via longitudinal grooves 37 a formedon the outer peripheral wall of plunger 37, via a through-hole 37 dformed at a central axis of plunger 37 and via a through-hole 39 formedin the sucking member 34.

A valve-closing spring 48 made of a conical compression spring forurging the valve rod 15′ upward is disposed at a lower portion (acooling medium outlet port 26) of the valve main body 20′. By the effectof urging force of this valve-closing spring 48, an upper end portion ofthe valve rod 15′ is always brought into press-contact with thethrough-hole 37 d portion of plunger 37.

A lower flange portion 35 a of the pipe 35 is mounted, through an O-ring57, on an upper end of the valve main body 20′. A flange (56 a)—attachedshort cylindrical pipe holder 56 is interposed between the flangeportion 35 a and the coil 32. These flange portions 35 a and 56 a areboth fixed to each other by means of the upper outer peripheralchamfering portion 29 of the valve main body 20′. An open bottom portion61 of the housing 60 is press-inserted in an upper end portion of thepipe holder 56. An upper end portion 62 of the housing 60 is calked tothe flange portion 31 c of the connector 31. An O-ring 66 is interposedbetween the housing 60 and the connector 31. At a lower central portionof the connector 31, there is formed a recessed portion 31 a in which aprojected portion 31 b to be engaged with the hexagonal hole of theadjusting screw 65 is formed. An upper portion of the stator 33 as wellas an upper portion of the adjusting screw 65 is inserted into thisrecessed portion 31 a.

In the control valve 5 constructed as described above, when the solenoidportion consisting of the coil 32, the stator 33 and the sucking member34 is electroexcited, the plunger 37 is drawn toward the sucking member34, forcing the valve rod 15′ to move upward (in the valve-closingdirection) by the urging force of the valve-closing spring 48. On theother hand, the cooling medium of suction pressure “Ps” that has beenintroduced into the suction pressure cooling medium-introducing ports 27from the compressor is introduced from the suction pressure coolingmedium-introducing chamber 23 into the pressure sensitive chamber 45 vialongitudinal grooves 37 a formed on the outer peripheral wall of plunger37 and via a through-hole 39 formed in the sucking member 34. As aresult, the bellows main body 40 (the interior thereof is kept invacuum) is caused to displace, i.e. contract or expand depending on thepressure (the suction pressure “Ps”) inside the pressure sensitivechamber 45 (when the suction pressure “Ps” is high, the bellows mainbody 40 is contracted, and when the suction pressure “Ps” is low, thebellows main body 40 is expanded). Then, this displacement istransmitted, via the operating rod 14 and the plunger 37, to the valverod 15′, thereby making it possible to adjust the magnitude of openingof valve (the effective cross-sectional area of passageway between thevalve seat 22 and the valve body 15 a). Namely, the magnitude of openingof valve will be determined depending on the sucking force of theplunger 37 to be effected by the solenoid portion consisting of the coil32, the stator 33 and the sucking member 34, on the urging force of thebellows main body 40, and on the urging force of the valve-openingspring 47 and the valve-closing spring 48. Further, depending on thismagnitude of opening of valve, the quantity (magnitude of restriction)of cooling medium of discharge pressure “Pd” that has been introducedfrom the discharge pressure cooling medium inlet port 25 into the valvechamber 21 and that will be delivered toward the outlet port 26, i.e.toward the crank chamber can be adjusted, thus making it possible tocontrol the pressure (cooling medium feeding pressure) “Pc” inside thecrank chamber.

The present inventors have attempted to develop a control valve which isapplicable to a compressor of large capacity while making it possible toshare, in order to reduce the manufacturing cost, the componentsemployed in the conventional control valves such as the aforementionedcontrol valve 5 for a variable capacity compressor. However, there arefollowing problems to be overcome in order to make the control valveapplicable to a compressor of large capacity.

Namely, in order to make the control valve applicable to a compressor oflarge capacity, it is necessary to enlarge the valve aperture 22 so asto increase the flow rate of cooling medium to be fed to the crankchamber of compressor from the cooling medium outlet port 26. However,if the valve aperture 22 is enlarged, the cooling medium outlet port 26side pressure (cooling medium feeding pressure “Pc” directed toward thecrank chamber) acting on the valve rod 15′ (valve body 15 a) would beincreased. In the case of the conventional control valve 5, a differencein pressure (Pc−Ps) between the cooling medium feeding pressure “Pc” andthe suction pressure “Ps” (acting on a top surface of the valve rod 15′)is so small that this difference is almost negligible in controlling theflow rate. However, when the flow rate of cooling medium is increased byenlarging the valve aperture 22 in order to make the valve applicable toa compressor of large capacity, the influence originating from thisdifference in pressure between the cooling medium feeding pressure “Pc”and the suction pressure “Ps” is increased, so that if theelectromagnetic actuator 30 and the pressure sensitive driving member40, each being the same in specifications, are employed (shared), thevalve rod 15′ (valve body 15 a) is pushed upward (valve closingdirection) due to this difference in pressure, thus giving badinfluences on the control of cooling medium flow rate.

Further, in the case of control valve 5 described above, since thepressure of cooling medium to be introduced into the valve chamber 21from the discharge pressure cooling medium inlet port 25 (dischargepressure “Pd”) is higher than the pressure of cooling medium in thesuction pressure cooling medium-introducing chamber 23 (suction pressure“Ps”), part of the cooling medium that has been introduced into thevalve chamber 21 is enabled to leak into the suction pressure coolingmedium-introducing chamber 23 through a slide-contacting interfacebetween the valve rod 15′ and the guide hole 19. As the quantity of thisleakage due to this difference (Pd>Ps) is increased, the control ofcooling medium would be badly affected. Therefore, it is desirable tominimize the quantity of this leakage due to this difference (Pd>Ps) asmuch as possible.

BRIEF SUMMARY OF THE INVENTION

The present invention has been made in view of the circumstancesmentioned above and, therefore, an object of the present invention toprovide a control valve for a variable capacity compressor, which isapplicable to a compressor of large capacity while making it possible toshare the components employed in other kinds of control valve.

With a view to achieving the aforementioned objects, there is provided,according to one aspect of the present invention, a control valve for avariable capacity compressor, which fundamentally comprises a valve mainbody equipped with a valve rod having a valve body, with a valve chamberhaving a guide hole in which the valve rod is enabled to slidinglyinsert and a valve aperture with which the valve body can beretractivebly contacted, with a cooling medium inlet port disposed on anupstream side of the valve aperture for introducing a cooling medium ofdischarge pressure from the compressor, and with a cooling medium outletport disposed on a downstream side of the valve aperture andcommunicated with a crank chamber of the compressor; an electromagneticactuator for driving the valve rod to move in the direction of openingor closing the valve aperture; and a pressure sensitive moving memberfor driving the valve rod to move in the direction of opening or closingthe valve aperture in response to a sucking pressure of the compressor.

Further, control valve is characterized in that a contracted holeportion is formed at an upper portion of the guide hole, that adiametrally reduced rod portion which can be slidingly inserted into thecontracted hole portion is formed at an upper portion of the valve rod,and that the valve rod is provided with an equalizing hole forintroducing a cooling medium pressure of the cooling medium outlet portinto an equalizing pressure introducing chamber which is interposedbetween an enlarged hole portion located below the contracted holeportion of the guide hole and a diametrally enlarged rod portion locatedbelow the diametrally reduced rod portion of the valve rod.

In a more preferable embodiment, the control valve for a variablecapacity compressor comprises a valve main body equipped with a valverod having a valve body, with a valve chamber having a guide hole inwhich the valve rod is enabled to slidingly insert and a valve aperturewith which the valve body can be retractivebly contacted, with a coolingmedium inlet port disposed on an upstream side of the valve aperture forintroducing a cooling medium of discharge pressure from the compressor,and with a cooling medium outlet port disposed on a downstream side ofthe valve aperture and communicated with a crank chamber of thecompressor; an electromagnetic actuator constituted by a coil, acylindrical stator disposed on the inner peripheral side of the coil, asucking member secured to the stator, and a plunger disposed below thesucking member and enabled to slide up and down; a pressure sensitivechamber which is formed on the inner peripheral side of the stator andover the sucking member and to which an inlet pressure is introducedtherein from the compressor; a pressure sensitive driving memberdisposed in the pressure-sensitive chamber; and an operating rodinterposed between a pressure sensitive driving member and the plunger;wherein the valve body is designed to be moved in the valve-closingdirection as the plunger is moved close to the sucking member and in thevalve-opening direction as the operating rod is pushed downward by theactuation of the pressure sensitive driving member; the control valvebeing further characterized in that a contracted hole portion is formedat an upper portion of the guide hole, that a diametrally reduced rodportion which can be slidingly inserted into the contracted hole portionis formed at an upper portion of the valve rod, and that the valve rodis provided with an equalizing hole for introducing a cooling mediumpressure of the cooling medium outlet port into an equalizing pressureintroducing chamber which is interposed between an enlarged hole portionlocated below the contracted hole portion of the guide hole and adiametrally enlarged rod portion located below the diametrally reducedrod portion of the valve rod.

In a further preferable embodiment, the valve rod is provided with anannular groove on an outer circumferential portion thereof which isdesigned to be slidingly contacted with the enlarged hole portion ofguide hole.

In the control valve for a variable capacity compressor according to thepresent invention, the pressure of the cooling medium outlet port sideacting on the valve body of valve rod (the pressure “Pc” to be fed tothe crank chamber) is transmitted, via equalizing hole formed in thevalve rod, into the equalizing pressure introducing chamber, enablingthe pressure “Pc” to act so as to push the valve rod downward, i.e. tominimize (cancel) the pressure difference between the cooling mediumfeeding pressure “Pc” and the suction pressure “Ps”. As a result, evenif the valve aperture is enlarged to increase the flow rate of coolingmedium in order to make the control valve applicable to a compressor oflarge capacity, it is possible to prevent the valve rod (valve body)from being pushed upward that might has been caused by the effect ofpressure difference between the cooling medium feeding pressure “Pc” andthe suction pressure “Ps”, thus overcoming the problems involved in thecontrol of valve. As a result, it is now possible to provide a controlvalve which is applicable to a compressor of large capacity while makingit possible to share the components employed in other kinds of controlvalve.

Further, part of the cooling medium that has been introduced into thevalve chamber from the discharge pressure cooling medium inlet port isenabled to enter into the equalizing pressure introducing chamberthrough a slide-contacting interface between the valve rod and the guidehole. In other words, since the leakage of cooling medium (from thedischarge pressure “Pd” to the suction pressure “Ps”) in theconventional control valve can be substantially prevented and hence thedischarge pressure “Pd” is allowed to pass toward the feeding pressure“Pc”, there is no possibility that the pressure control can be badlyaffected. As a result, it is possible to enhance the accuracy ofpressure control.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view illustrating one embodiment ofthe control valve for a variable capacity compressor according to thepresent invention;

FIG. 2 is an enlarged longitudinal sectional view illustrating a mainportion of the control valve shown in FIG. 1; and

FIG. 3 is a longitudinal sectional view illustrating one example of thecontrol valve for a variable capacity compressor according to the priorart.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, a specific embodiment of the control valve for a variable capacitycompressor according to the present invention will be explained indetail with reference to the drawings.

FIG. 1 shows a longitudinal sectional view illustrating one embodimentof the control valve for a variable capacity compressor according to thepresent invention.

The control valve 1 for a variable capacity compressor shown in FIG. 1is designed such that it is applicable to a compressor of large capacitywhile making it possible to share the components such as theelectromagnetic actuator 30, the pressure sensitive moving member(bellows main body) 40, etc. of the conventional control valve 5 for avariable capacity compressor which is shown in FIG. 3. In the followingdescription, the parts or components which correspond to those of theconventional control valve 5 for a variable capacity compressor which isshown in FIG. 3 will be identified by the same reference numbers and thefeatures which differ from those of the conventional control valve 5will be mainly explained.

The control valve 1 shown in FIG. 1 comprises a valve main body 20 whichis equipped with a valve rod 15 having a valve body 15 a which is cross-or T-shaped in cross-section (to be explained hereinafter in moredetail), with a valve chamber 21 provided with a valve seat (valveaperture) 22 with which the valve body 15 a can be retractiveblycontacted, with a plurality of cooling medium inlet ports 25 forintroducing a cooling medium of discharge pressure “Pd” from thecompressor into the outer peripheral portion of the valve chamber 21 (onthe upstream side of the valve seat 22), and with a cooling mediumoutlet port 26 disposed below (downstream side of) the valve seat 22 andcommunicated with the crank chamber of compressor; and anelectromagnetic actuator 30.

The electromagnetic actuator 30 is equipped with an electromagnetic coil32 having a connector 31 for electroexcitation, a step-attachedcylindrical stator 33 disposed on the inner peripheral side of theelectromagnetic coil 32, a sucking member 34 having U-shapedcross-section and press-inserted into a lower inner peripheral endportion of the stator 33, a plunger 37 slidingly disposed to move up anddown in a guide pipe 35 and located below the sucking member 34, thecylindrical guide pipe 35 for guiding the plunger 37, which is fixedlycoupled, through a brazing which is applied to an upper inner peripheralend 35 a, to a lower outer peripheral end portion of the stator 33, astep-attached cylindrical housing 60 disposed covering the outerperipheral portion of the coil 32, and a short cylindrical holder 50interposed between an upper end portion of the valve main body 20 andthe coil 32.

A lower end portion of the pipe 35 is fitted inside the holder 50 andfixedly coupled thereto by means of brazing. A lower diametrallycontracted portion 61 of the housing 60 is externally inserted over anouter peripheral portion of holder 50. An upper end portion 62 of thehousing 60 is calked to nearly an upper end portion of the coil 32. At alower end portion of the holder 50, there is integrally formed a thinwall flanged cylindrical portion 50 a which is externally fitted on anupper outer peripheral wall of the valve main body 20. The holder 50 isfixed to the valve main body 20 through the peel-calking work of thecylindrical portion 50 a.

Additionally, a hexagon socket head adjusting screw 65 is screwed on anupper portion of the stator 33. A pressure sensitive chamber 45 intowhich the sucking pressure “Ps” of compressor is to be introduced isformed between the adjusting screw 65 attached to the inner peripheralwall of stator 33 and the sucking member 34. In this pressure sensitivechamber 45, there are disposed, as a pressure sensitive driving member,a bellows main body 40 consisting of a bellows 41, a downwardlyprojected upper stopper 42, a reverse U-shaped lower stopper 43 and acompression coil spring 44. Further, a compression coil spring 46 forurging the bellows main body 40 to contract (in the direction tocontract it toward the adjusting screw 65) is interposed between thebellows main body 40 and the sucking member 34. Further, a step-attachedoperating rod 14 piercing through the sucking member 34 is interposedbetween the reverse U-shaped lower stopper 43 and a U-shaped portion 37c of plunger 37. Additionally, a valve-opening spring 47 made of acompression coil spring for urging the valve rod 15 downward (in thedirection to open the valve) by way of the plunger 37 is interposedbetween the sucking member 34 and the U-shaped portion 37 b of plunger37.

On the other hand, a convex stopper 28 for regulating the lowermostdescending position of the plunger 37 is projected from an upper centralportion of the valve main body 20. A guide hole 19 (to be described indetail hereinafter) in which the valve rod 15 is slidingly inserted isformed at a central portion of the valve main body 20 which is locatedover the valve chamber and also at a central portion of the convexstopper 28. A suction pressure cooling medium-introducing chamber 23into which the cooling medium of suction pressure “Ps” of compressor isformed between the plunger 37 and an upper outer periphery of the valvemain body 20 (an outer peripheral wall of the convex stopper 28). Aplurality of suction pressure cooling medium-introducing ports 27 areformed in the outer wall of the suction pressure coolingmedium-introducing chamber 23. A cooling medium of sucking pressure “Ps”that has been introduced into the suction pressure coolingmedium-introducing chamber 23 from the cooling medium-introducing ports27 is designed to be introduced into the pressure sensitive chamber 45via longitudinal grooves 37 a formed on the outer peripheral wall ofplunger 37, via a through-hole 37 d formed at a central axis of plunger37 and via a through-hole 39 formed in the sucking member 34. At thesame time, this sucking pressure “Ps” is enabled to act on a top surfaceof the valve rod 15.

A valve-closing spring 48 made of a conical compression spring forurging the valve rod 15 upward to press an upper end portion of valverod 15 against the through hole 37 d portion of plunger 37 is disposedin the cooling medium outlet port 26 disposed at a lowermost portion ofthe valve main body 20.

In the control valve 1 of this embodiment, the diameters of the valveaperture 22, the valve rod 15 and the guide hole 10 are all made largerthan those of the control valve 5 shown in FIG. 3 described above so asto make the control valve 20 applicable to a compressor of largecapacity. Further, as clearly seen from FIG. 1 and FIG. 2 (partiallyenlarged), a contracted hole portion 19 b is formed at an upper portionof the guide hole 19, and a diametrally reduced rod portion 15 b whichcan be slidingly inserted into the contracted hole portion 19 b isformed at an upper portion of the valve rod 15. The valve rod 15 isprovided with an equalizing hole 51 for introducing a cooling mediumpressure “Pc” of the cooling medium outlet port 26 into an equalizingpressure introducing chamber 52 which is interposed between an enlargedhole portion 19A located below the contracted hole portion 19 b of theguide hole 19 and a diametrally enlarged rod portion 15A located belowthe diametrally reduced rod portion 15 b of the valve rod 15. Thisequalizing hole 51 extends, piercing through the axis of the valve rod15, from a lower end of the valve rod 15 up to an upper portion of thevalve rod 15 which is located near the diametrally reduced rod portion15 b. A plurality of lateral holes opening to the equalizing pressureintroducing chamber 52 are formed at an upper portion of the valve rod15. On an outer circumferential portion of the enlarged hole portion 19Aof valve rod 15 (a lower end portion of the valve rod 15), which isadapted to be slidingly contacted with the guide hole 19, there areformed three annular grooves 15 c.

In the control valve 1 constructed as described above, when the solenoidportion consisting of the coil 32, the stator 33 and the sucking member34 is electroexcited, the plunger 37 is drawn toward the sucking member34, forcing the valve rod 15 to move upward (in the valve-closingdirection) by the urging force of the valve-closing spring 48. On theother hand, the cooling medium of suction pressure “Ps” that has beenintroduced into the cooling medium-introducing ports 27 from thecompressor is introduced from the suction pressure coolingmedium-introducing chamber 23 into the pressure sensitive chamber 45 vialongitudinal grooves 37 a formed on the outer peripheral wall of plunger37 and via a through-hole 39 formed in the sucking member 34. Thebellows main body 40 (the interior thereof is kept in vacuum) is causedto displace, i.e. contract or expand depending on the pressure (thesuction pressure “Ps”) inside the pressure sensitive chamber 45 (whenthe suction pressure “Ps” is high, the bellows main body 40 iscontracted, and when the suction pressure “Ps” is low, the bellows mainbody 40 is expanded). Then, this displacement is transmitted, via theoperating rod 14 and the plunger 37, to the valve rod 15, thereby makingit possible to adjust the magnitude of opening of valve (the effectivecross-sectional area of passageway between the valve aperture 22 and thevalve body 15 a). Namely, the magnitude of opening of valve can bedetermined depending on the sucking force of the plunger 37 to beeffected by the solenoid portion consisting of the coil 32, the stator33 and the sucking member 34, on the urging force of the bellows mainbody 40, and on the urging force of the valve-opening spring 47 and thevalve-closing spring 48. Further, depending on this magnitude of openingof valve, the quantity (magnitude of restriction) of cooling medium ofdischarge pressure “Pd” that has been introduced from the dischargepressure cooling medium inlet port 25 into the valve chamber 21 and thatcan be delivered toward the cooling medium outlet port 26, i.e. towardthe crank chamber can be adjusted, thus making it possible to controlthe pressure “Pc” (feeding pressure) inside the crank chamber.

In the control valve 1 for a variable capacity compressor according tothis embodiment, the pressure of the cooling medium outlet port sideacting on the valve body 15 a of valve rod 15 (the pressure “Pc” to befed to the crank chamber) is transmitted, via the equalizing hole 51formed in the valve rod 15, into the equalizing pressure introducingchamber 52, enabling the pressure “Pc” to act so as to push the valverod 15 downward, i.e. to minimize (cancel) the pressure differencebetween the cooling medium feeding pressure “Pc” and the suctionpressure “Ps”. As a result, even if the valve aperture 22 is enlarged toincrease the flow rate of cooling medium in order to make the controlvalve applicable to a compressor of large capacity, it is possible toprevent the valve rod (valve body) from being pushed upward that mighthas been caused by the effect of pressure difference between the coolingmedium feeding pressure “Pc” and the suction pressure “Ps”, thusovercoming the problems involved in the control of valve. As a result,it is now possible to provide a control valve which is applicable to acompressor of large capacity while making it possible to share thecomponents employed in other kinds of control valve.

Further, part of the cooling medium that has been introduced into thevalve chamber 21 from the discharge pressure cooling medium inlet port25 is enabled to enter into the equalizing pressure introducing chamber52 through a slide-contacting interface between the diametrally enlargedrod portion 15A of valve rod 15 and the enlarged hole portion 19A ofguide hole 19. In other words, since the leakage of cooling medium (fromthe discharge pressure “Pd” to the suction pressure “Ps”) in theconventional control valve can be substantially prevented and hence thedischarge pressure “Pd” is allowed to pass toward the feeding pressure“Pc”, there is no possibility that the pressure control can be badlyaffected. As a result, it is possible to enhance the accuracy ofpressure control.

Further, since the annular grooves 15 c are formed on the valve rod 15,it is possible to minimize the leakage of pressure from the dischargepressure “Pd” to the feeding pressure “Pc” due to the labyrinth effectsby these annular grooves 15 c. At the same time, due to the provision ofannular grooves 15 c, it is possible to entrap fine foreign matters thatmay be intruded into the sliding interface between the valve rod 15 andthe guide hole 19. As a result, the clogging of the sliding interfacebetween the valve rod 15 and the guide hole 19 due to fine foreignmatters can be prohibited, thus obviating the operation failure of valverod 15, e.g. the trouble of valve rod 15 where the valve rod 15 isprevented from moving upward, thus leaving it behind even if the plunger37 is attracted toward the sucking member 34.

1. A control valve for a variable capacity compressor, comprising: avalve main body including a valve rod having a valve body, the valve rodhaving a diametrally reduced rod portion formed at a first portionthereof and a diametrally enlarged rod portion formed at a secondportion thereof, a valve chamber having a guide hole for receiving thevalve rod and a valve aperture with which the valve body is capable ofbeing contacted, the guide hole having a contracted hole portion formedat a first portion thereof and an enlarged hole portion formed at asecond portion thereof, a cooling medium inlet port disposed on anupstream side of the valve aperture for introducing a cooling medium ofdischarge pressure from the compressor, and a cooling medium outlet portdisposed on a downstream side of the valve aperture and capable ofcommunicating with a crank chamber of the compressor; an electromagneticactuator for moving the valve rod in a direction of opening or closingthe valve aperture; and a pressure sensitive moving member for movingthe valve rod in the direction of opening or closing the valve aperturein response to a sucking pressure of the compressor; wherein thediametrally reduced rod portion is adapted to be slidingly inserted intothe contracted hole portion, and the valve rod includes an equalizinghole for introducing a cooling medium pressure of the cooling mediumoutlet port into an equalizing pressure introducing chamber within thevalve main body.
 2. A control valve for a variable capacity compressor,which comprises: a valve main body including a valve rod having a valvebody, the valve rod having a diametrally reduced rod portion formed at afirst portion thereof and a diametrally enlarged rod portion formed at asecond portion thereof, a valve chamber having a guide hole forreceiving the valve rod and a valve aperture with which the valve bodyis capable of being contacted, the guide hole having a contracted holeportion formed at a first portion thereof and an enlarged hole portionformed at a second portion thereof a cooling medium inlet port disposedon an upstream side of the valve aperture for introducing a coolingmedium of discharge pressure from the compressor, and a cooling mediumoutlet port disposed on a downstream side of the valve aperture andcapable of communicating with a crank chamber of the compressor; anelectromagnetic actuator including a coil, a cylindrical stator disposedon the inner peripheral side of the coil, a sucking member secured tothe stator, and a plunger capable of cooperating with the coil andmoving the valve rod in a direction of opening or closing the valveaperture; a pressure sensitive chamber which is formed on the innerperipheral side of the stator and over the sucking member and to whichan inlet pressure is introduced therein from the compressor; a pressuresensitive driving member disposed in the pressure-sensitive chamber; andan operating rod interposed between a pressure sensitive driving memberand the plunger; wherein the valve body is designed to be moved in thevalve-closing direction as the plunger is moved in a first direction andthe valve body is designed to be moved in the valve-opening direction asthe operating rod is pushed in a direction opposite the first directionby the actuation of the pressure sensitive driving member; wherein thediametrally reduced rod portion is adapted to be slidingly inserted intothe contracted hole portion, and the valve rod includes an equalizinghole for introducing a cooling medium pressure of the cooling mediumoutlet port into an equalizing pressure introducing chamber within thevalve main body.
 3. The control valve of claim 1 wherein the equalizingpressure introducing chamber comprises an area between the contractedhole portion and the enlarged rod portion.
 4. The control valve of claim2 wherein the equalizing pressure introducing chamber comprises an areabetween the contracted hole portion and the enlarged rod portion.
 5. Thecontrol valve of claim 1, wherein the valve rod includes an annulargroove on an outer circumferential portion thereof designed to slidinglycontact the enlarged hole portion of guide hole.
 6. The control valve ofclaim 2, wherein the valve rod includes an annular groove on an outercircumferential portion thereof designed to slidingly contact theenlarged hole portion of guide hole.
 7. The control valve of claim 3,wherein the valve rod includes an annular groove on an outercircumferential portion thereof designed to slidingly contact theenlarged hole portion of guide hole
 8. The control valve of claim 4,wherein the valve rod includes an annular groove on an outercircumferential portion thereof designed to slidingly contact theenlarged hole portion of guide hole.